[Howto] Git Cherry Pick From Pull Requests

[Lolonois]

This short sketch outlines the process to try pull requests (PR) before they are merged into the master. I am using RetroPie-Setup and PR 3126 as sample but it is not limited to this repo/PR. Works the same on any git(hub) repo.

On your RetroPie as user pi:

1. Change to folder: cd ~/RetroPie-Setup

2. Update your local repo to remote origin/master: Run git pull

3. Create a branch with all changes of a pull request (replace 3126 with your specific PR you want to try) (ahead and behind origin/master): git fetch origin pull/3126/head:PR_3126

4. List commits where PR is ahead of current master: git log HEAD..PR_3126 (Should list one commit: e5665ae90a0d1bacd3f904194bb263a93cd2d19d)

5. Create a new branch to hold the "ahead commits": git checkout -b lrvice_moretargets_cherries

6. Put the cherry (or cherries if more than one commit) in your basket, errm. branch: git cherry-pick e5665ae (first seven characters of above commit are sufficient)

7. Side note: Now you may understand why it is useful to have a PR squished to one commit. ;)

8. Optional: Check if it worked: git diff origin/master output should start like this:

   diff --git a/scriptmodules/libretrocores/lr-vice.sh b/scriptmodules/libretrocores/lr-vice.sh
   index 53f7cb8d..553fdeb6 100644
   --- a/scriptmodules/libretrocores/lr-vice.sh
   +++ b/scriptmodules/libretrocores/lr-vice.sh
   @@ -10,37 +10,57 @@
    #
   
    rp_module_id="lr-vice"
   -rp_module_desc="C64 emulator - port of VICE for libretro"
   -rp_module_help="ROM Extensions: .cmd .crt .d64 .d71 .d80 .d81 .g64 .m3u .prg .t64 .tap .x64 .zip .vsf\n\nCopy your Commodore 64 games to $romdir/c64"
   +rp_module_desc="C64 / C128 / PET / Plus4 / VIC20 emulator - port of VICE for libretro"
   +rp_module_help="ROM Extensions: .cmd .crt .d64 .d71 .d80 .d81 .g64 .m3u .prg .t64 .tap .x64 .zip .vsf\n\nCopy your games to $romdir/c64"
    rp_module_licence="GPL2 https://raw.githubusercontent.com/libretro/vice-libretro/master/vice/COPYING"
    rp_module_repo="git https://github.com/libretro/vice-libretro.git master"
    rp_module_s[...]
   

9. Use retropie_setup.sh / retropie_packages.sh scripts as usual

10. Smile (:

Final notes

• Reverting as easy as: git checkout master, that's all.
• If you wish, you can still return to the version of the PR with git checkout lrvice_moretargets_cherries.
• If you forgot the branch name or uncertain on which branch you are: git branch -l is your friend.
• If you want to get rid of your cherrypicked branch do git branch -D lrvice_moretargets_cherries.